Neat find. I have seen some like this with parts of the old wooden pipes still attached although wood in your area might be too valuable a commodity to just abandon once the flume was no longer in use. Any clues what the flume was used for?
There is an issue with Uploading Photos (attachjments). I am not sure what the problem is, and I am looking into it. You can still try to Create your Threads and Upload your Photos, but it is hanging up during the Upload.